Description: (Applicant's Description) Transgenic and knock-out mice have assumed increasing importance as an experimental system for cancer research in recent years. These technologies have important contributions to make to numerous investigators many of whom may not have a background in the necessary techniques. The goal of the Transgenic Mouse Core Facility is to make these important technologies available to the cancer research community. The facility provides two basic services, 1) direct microinjection of DNA into the male pronucleus of the mouse zygote to make transgenic mice; and 2) microinjection of targeted ES cells into the blastocoel of the 3.5 day mouse embryo to make chimeric mice, an important step in the production of targeted disruption of a gene.